Screw-threaded connection



L. J. VOORHEES.

SCREW THREADED CONNECTION.

APPLICATION FILED MAY 29, 1920.

1,388,622. Patented g- 23, 1921.

UNITED STATES PATENT OFFICE.

LEE 3'. VOORHEES, OF IBING-HAMTON, NEW YORK, ASSIGNOR TO NATIONAL CARBONCOMPANY, INC., A. CORPORATION OF NEW YORK.

SCREW-THREADED CONNECTION.

To all wlmm it may concern:

Be it known that 1, LEE J. VOORHEES, a citizen of the United States,residing at Binghamton, in the county of Broome and State of New York,have invented certain new and useful Improvements in Screw- ThreadedConnections, of which the following is a specification.

This invention relates to screw-threaded connections between membersformed of materials exhibiting different changes of dimensions under theinfluence of the same change in conditions. The invention also includesthe process of making the connections referredto above.

The object of the invention is to provide a form of connection in whichthe connected parts will neither seize nor become excessively loose whenthey undergo unequal expansion or contraction.

It is well known that various materials are unequally affected bychanges in the corn dition to which they are exposed. For example, if apiece of wood has attained a constant length in an atmosphere containinga large percentage of water vapor and the content of water vapor is thenreduced, other conditions remaining the same, the piece of wood willcontract or shrink. A piece of metal subjected to the same change wouldnot be altered in length. Likewise an increase in temperature will causea piece of metal to expand more than a piece of the same size made frommany non-metallic materials, and there isa material difference among thevarious metals with respect to their temperature-dimension relations.Changes in pressure can also affect different solid materials unequally.

When it is necessary to join unlike materials by a screw-threaded jointwhich is to be subjected to changes of conditions, the dimensions of theparts must be such that t the connection will still be preserved when anunfavorable extreme condition is encountered. Furthermore, if the partsare to be joined so that they can be readily separated under allconditions, the parts must be of such sizes that they will not seizeunder extremes of expansion and contraction. If due allowance is madefor extremes winch favor seizing of the parts, the connection is apt tobe loose and unreliable under all other conditions. Specific in-Specification of Letters Patent. Patented Aug. 23, 1921.

Application filed May 29,

1920. Serial No. 385,378.

stances of this nature are found in cases where male-threaded members ofwood or the like are fitted to female-threaded members of metal, orwhere male-threaded members of metals of low expansion such as iron, arefitted to female-threaded members of metals of high expansion, such ascopper or aluminum. The former joints are likely tobe tootight in dampweather and too loose in dry, while the latter joints will be too tightwhen cold and too loose when hot.

As a further specific instance of the effect of changes of atmosphericcondition upon a joint connecting parts of dissimilar mate rial, it maybe. said that it has heretofore been regarded as impractical to attachthe usual metal end ca of a flashlight directly to the casing of t elight by means of a screw-thread when the casing is made of fiber orother material which is subject to dimension changes under the influenceof changing atmospheric conditions, for example, variation in themoisture content of the atmosphere. When it has been attempted to sodirectl thread together metal ca s and fiber casings, it has been foundthat in dry weather the fiber becomes so contracted that the joint isloose and unreliable, while in very damp weather, the fiber casin becomes so expanded that the casing an ca will become seized and may beseparate only with the greatest difficulty.

0 provide between such dissimilar materials a connection which will notseize under the extreme conditions favoring a close fit and which willnot become loose under the opposite extreme of conditions, I havedesigned the form of connection hereinafter described, two specificexamples of my invention being shown in the accompanying drawings, inwhich- Figure 1 shows a threaded metal cap directly attached to thethreaded tubular fiber casingof a flashlight,

Fig. 2 shows an end View of the flashlight The flashlight shown in Fig.I is of a general and well known construction and only those parts whichcomprise my improvement will be described.

The casing 6 for holding the battery is of fiber as already mentioned.The end-cap 7 for retaining the battery in the casing, is of metal.According to the prior practice, it has been found necessary to attachto the end of the fiber casing, a threaded ring, for

dition will be reached after continued explosure to air saturated withwater vapor. pon a change to dryer atmosphere, the top 6 will shrink andin the absence of special provisions to prevent its receding from themetal cap 7, 1t would, under conditions of extreme dryness, become soshrunken that the joint between the tube and cap 7 would be worthlessfrom a practical point of view.

To revent the casing 6 from receding from t e cap 7, when'the casingundergoes contraction, I have provided a special form of end-cacomprising inclined surfaces 9 which wil engage the end of the tubularcasing 6 upon application of the cap, and expand it against the threadsof the metal cap provided a shrinkage of the tubing has already takenplace. If the tube 6 1s already at its full size, the inclined surfacewill merely engage its end without enlarg-- ing its diameter. Whether ornot the tube was at its full size when the parts were assembled, whenthe 'cap 7 is turned to the limit of its motion on the screw-thread, theinner corner of the lower extremity of the tube will be engaged by theinclined surface 9 1n such a way that the top of the tube may shrinkwithout any possibility of the lower end, comprising the greater part ofthe screw-thread, being able to recede from the metal cap. A shghtrecession may take place near the top of the metal cap, as best shown inFig. 4, but since the threads will be in contact throughout aconsiderable proportion of their length, this will be Sllfilr cient tomaintain the joint in a tight and satisfactory condition, in spite ofthe shrinkage of the body of the tube. The slots 8 will ermit areduction of cross-section of the her tube in its unrestrained portionswhile the original cross-section is maintained at its lower end withoutsplitting the tube, because'of the increased resiliency provided by saidslots; A similar construction mahy be used at the lamp-end of thecasing. rom the foregoing, the operation of the joint shown in Fig. 5will be readily understood. In this figure the tube 10 is formed fromametal having a low coefiicient of expansion and is rovided at its endwith a female-thread. he tube 11 is formed from a metal havingrelatively high coeflicient of expansion and is provided with amalethread enga ing the thread on'tube 10, an inclined sur aceperforming the same function as the surface 9 of Fig. 1, being providedby the internally projecting flange 12 inside the tube 10 at theextremity of the thread with which tube 10 is provided. The slots 13 intube 11 perform a function exactly similar to the function of slots 8 inFi s. l and 2.

' ssuming that the joint of Fig. 5 is designed to be tight at a certainhigh temperature, and that the parts must not be seized at thistemperature, the tubes are so proportioned that a perfect fit will beattained when the connected tubes have acquired the dimensionscorresponding to this temperature. If the jointis then subjected tolower temperature, the tube 11 will contract more than the tube 10 andthere will be a tendency for the threads to become separated, especiallynear the extremity of tube 10. However, the reater part of the engagingthreads wil continue to be held in close contact by means of theinclined surface 12, and the loosening of the joint, which will followthe decrease in temperature, will not be greater than is permissibleunder the circumstances.

While the invention has been illustrated in its application to certainspecific cases where a screw-thread joint or connection be tween partsofdissimllar materials is desirable, it will be apparent that theinvention may be applied to a great variety of connections and may beemployed where er one of the materials is in tubular form, elasticenough to undergo slight fiexure without breaking, stiff enoughsubstantially to maintain its original form in spite of the defor-'mation of its end by a wed 'ng action, and capable of taking a screw-tread.

I claim:

1. A connection which com rises a tubular member of a material WhlCh isstiff but flexible, said tubular member having a screwthread and beingprovided with slots to increase its resiliency, a second member of amaterial diflering from the material of the tubular member in the changeof dimensions which it exhibits under the influence of the same changein conditions, a screw-thread on said second member enga ing thescrewthread on the tubular mem er, and means to hold portions oftherespective screwtive changes in the dimensions of the connected members.

2. A connection which comprises a tubular member of a material which isstiff but flexible, said tubular member having a screw-thread and beingprovided with slots to increase its resiliency, a second member of amaterial differing from the material of the tubular member in the changeof dimensions which it exhibits under the infiuence of the same changein conditions, a

screw-thread on said second member engag ing the screw-thread on thetubular member, and an inclined surface attached to said second memberand adapted to hold portions of the respective screw-threads in closecontact regardless of relative chan es in the dimensions of theconnected mem ers.

3. A connection which comprises a'tubular member of fiber or the like,said tubular member being provided with slots to increase crease itsresiliency, a metal cap, a screwthread on said metal cap engaging thescrewthread on the tubular member, and an inclined surface forming apart of the metal cap andadapted to hold portions of the screw-thread inclose contact regardless of shrinkage of the tubular member.

5. Process of connecting a screw-threaded tubular member to a secondmember made of material differing from the material of the tubularmember in the change of dimensions which it exhibits under the influenceof the same change in conditions, which comprises forming on the secondmember a screwthread adapted to engage the thread of said tubularmember, cutting the end of the tubular member to increase itsresiliency, providing an inclined surface attached to said second memberand adapted to force and hold the respective threaded portions in closercontact when the members'are screwed together, and then screwing themembers togethen' 6. Process of connecting a screw-threaded tubularmember to asecond member made of a material differing from the materialof the tubular member in the change of dimensions which it exhibitsunder the influence of the same change. in conditions, which comprisesforming on the second member a screw-thread adapted to engage the threadof said tubular member, slotting the end of the tubular member toincrease its resiliency, forming on said second member an inclinedsurface adapted to force and hold the re-.

spective threaded portions in closer contact when the members arescrewed together,'and then screwing the members together.

In testimony whereof, I affixmy signature.

LEE J. VOORHEES.

